Calculating volt drop for >16mm cable

[BillySangster]

Hello there.
I'm trying to calculate the volt drop on cables that are over 16mm csa using the tables in BS7671. It's quite easy for lower sized cables, (length x design current x mV/A/m, if I'm right) but what happens when you go above 16mm and have a resistive component mV/A/m(r), reactive component mV/A/m(x) and inductive component mV/A/m(z)? Do I take all of these into account, or just choose according to load type? The regs aren't really very clear on this bit, I'm finding.

 

[telectrix]

if you look at table 6E2 in the red osg, page 133, you will see that the mV/A/m includes the reactive elements for cables 25mm and above. so it's a straightforward calculation.

 

[ackbarthestar]

mV/A/m(z) = assumed impedance Z= rt(R^2 + x^2)
The assumed loading (current flow) on a large cable will generate its own inductive reactance, so needs to be taken into consideration

 

[BillySangster]

mV/A/m(z) = assumed impedance Z= rt(R^2 + x^2)
The assumed loading (current flow) on a large cable will generate its own inductive reactance, so needs to be taken into consideration

Ah right, so because mv/A/m(z) is using both the reactive and resistive components to be formulated, this is the value to use in the volt drop calculation.
Thanks.